Optical systems often utilize optical fibers to transport optical signals and optical powers between system components or to a workpiece. Coupling light into fibers for subsequent transport presents several technical challenges that must be overcome. Incident light and optical fiber characteristics, such as wavelengths, numerical apertures, core and cladding features, refractive indices, etc., determine in significant part what and how much light may be coupled into an optical fiber. As incident optical powers increase, even with perfect alignment conditions, additional problems can arise. In some situations, those problems can lead to catastrophic failure in proximity to the coupling between the incident light and the optical fiber, at other portions of the fiber termination assembly, as well as at other components of the optical system connected to the fiber termination assembly.
In U.S. Pat. No. 6,282,349 to Griffin a launch fiber termination discloses a silica or quartz ferrule having a bore in which an optical fiber is inserted and heat fused to the interior bore surface. A beam block has an extension that surrounds a polymer jacket of the inserted fiber and is crimped onto the jacket. In general, use of epoxy is to be avoided since it tends to contaminate a laser output lens, and is prone to explosive failure. While epoxy may be convenient for construction of various termination assemblies, epoxy failures become more likely at higher energy levels leading to further restriction on use. Moreover, different work-arounds have been employed to mitigate failures while preserving the utility of epoxy. For example, multiple adhesives may be used, such as temporary adhesives. However, the yield advantages of epoxy-type terminations tend to be lost as the process becomes more complex. Additionally, these approaches tend to require removal of the outer cladding which should not be removed since it performs a cladding role in maintaining internal reflection. Accordingly, it has remained a challenge in the art of fiber termination to provide a high-yield solution for high-power applications.